This invention is concerned generally with the attachment of a loop to an apertured device e.g. an implantable device for use in the itmplantation of a prosthetic ligament.
In the implantation of a prosthetic ligament in a bone joint e.g. the knee joint between tibial and femoral components, it is usual to drill tunnels through the bones, and to pull the prosthetic ligament through the tunnels until a required position is reached within the joint, followed by suitable anchoring of the ligament against linear movement in either direction. The anchoring may involve use of bone staples or other intrusive fixations, which attach tensile elements (connected to each end of the ligament) to suitable bone sites adjacent to the mouths of the bone tunnels.
Prosthetic ligaments can be made of synthetic material, provided that it is of suitable implantable nature, and which may be woven, although autogenous tissue harvested from the patient is the more popular method.
One more recent endoscopic technique which has been developed in ACL reconstruction (anterior cruciate ligament reconstruction), involves use of an attachment device which serves both to guide the implantation of the ligament, and to secure one end of the ligament against axial movement in one direction, but the attachment device is of such a construction that it does not need to anchor itself in position by physical intrusion into the bone.
The attachment device used in the technique provides easy guidance of the ligament, by forming the lead element of a trailing implantation system, and which passes through the usual drilled-out bone tunnels, and then upon exiting of the lead element from an upper mouth of one of the tunnels i.e. when it projects upwardly out of the femoral component, a simple manipulation of the device causes it to overlie the mouth of the tunnel, and thereby provide tensile restraint for the ligament end of the now implanted ligament to which it is attached.
The attachment device therefore is capable of being manipulated between a pulling position, in which it has reduced lateral extent relative to the pulling direction, and to an anchoring position in which it has maximum lateral extent relative to the pulling direction.
This known attachment device (known as an endobutton) comprises a small metal bar which is about 12 mm in length, 4 mm wide and 1.5 mm in thickness, and has a row of four circular holes extending through it, of which the two outermost holes serve for attachment of two separate pulling sutures, and the inner pair of holes serve to attach the metal bar to the trailing ligament via a further set of sutures. The set of pulling sutures is taken first through the lower end of the lowermost bone tunnel in the tibial component and then passes upwardly through the bone tunnel in the femoral component, and pulls the trailing ligament system behind it. In practice only one of the sutures has tension applied to it sufficient to pull the metal bar behind it with the bar manipulating itself to take-up the pulling position of reduced lateral projection, and to be pulled lengthwise through the tunnels. Since the bar orientates itself so that its longitudinal axis aligns itself with the pulling direction, the diameter of the final passage drilled through the femoral component can be reduced, compared with the larger diameter of the tunnel which is formed so as to receive the implanted ligament. This final passage therefore can have a diameter of slightly more only than the maximum transverse dimension of the bar (4 mm). Upon exiting from the femoral component, the other pulling suture is then operated so as to manipulate the bar to take-up a transverse position in which its longitudinal axis is generally perpendicular to the passage whereby it can overlie the exit mouth of the small diameter passage. Downward tension applied to the trailing assembly attached to the bar then anchors the attachment bar in position in a non-intrusive manner with respect to the surrounding bone.
The trailing assembly which follows the pulling-through of the attachment bar usually comprises (a) further sutures which are taken through the central pair of holes in the bar, and then connected together to complete the formation of a loop by knotting together of the ends of the sutures, and (b) the prosthetic ligament which is attached to the looped sutures in any convenient manner.
In the case of harvested tissue which comprises tendon material and boney material (plugs) attached at each end of the tendon material, the sutures are taken through holes formed in one of the bone plugs and then knotted to complete the formation of the attachment loop.
The present invention is concerned with the use of different material to form an attached loop to the existing use of sutures knotted together, as referred to above, and utilises flexible and implantable material assembled from a loosely structured fibre bundle of twisted yarn. In particular, the present invention is concerned with a method and device for the simultaneous formation and attachment of the loop (comprising a loosely structured fibre bundle) to an apertured device, so as to speed-up the attachment of the loop and thereby derive the benefits of mass production techniques, compared with existing purely manual manipulations which are employed in order to attach a loop to an apertured device.
According to one aspect of the invention there is provided a method for the simultaneous formation and attachment of a loop to an apertured device, in which the loop is formed from a loosely structured fibre bundle of twisted yarn, and the device has first and second apertures through which the loop can be taken, in which the method comprises:
withdrawing a leading end of yarn from a yarn supply and feeding the leading end through the first aperture in one direction, and through the second aperture in an opposite direction;
taking the leading end of yarn away from the device and along a guide path so as to form a basic loop;
withdrawing further yarn from the supply simultaneously with applying movement of the basic loop along the guide path so as to apply successive loop turns to the basic loop and therefore form a progressively increasing loop core; and,
applying relative twist between the loop core and each successive loop turn so as to form a cohesive looped fibre bundle attached to the device.
The method of the invention therefore automates the production of a device with attached loop, and allows a greatly increased rate of manufacture as compared with purely manual manipulation methods used to date.
Preferably, the initial xe2x80x9cthreading throughxe2x80x9d of the yarn through the device is carried out by manual manipulation, and the subsequent completion of the basic loop, but thereafter the operation can be automatic.
The basic loop can be completed by any suitable technique, and conveniently the leading end is joined to the trailing end of the loop (having just issued from the yarn supplied) by heat fusion e.g. light application of a heating head to the leading end. The basic loop can then be caused to carry out successive orbits of its closed path while further loop turns are applied thereto, and the progressively increasing loop core also is then caused to carry out successive orbits while further loop turns are applied thereto.
Preferably, rotatable capstans are arranged along the closed path, and engage the basic loop (and the increasing loop core), Lo drive it along the closed loop while further yarn is withdrawn from the supply.
Relative twist between the loop core and successive loop turns may be obtained by one of three techniques, namely:
1. causing the loop core to pass through a bobbin supply of yarn (forming part of the closed guide path), and rotating the bobbin about this portion of the closed path while yarn is withdrawn;
2. withdraw yarn off the end of a stationary bobbin (PIRN); and,
3. applying twisting movement to the loop core as it moves along the closed path, simultaneously with application of yarn from the supply to the circumference of the rotating loop core.
According to a further aspect of the invention, there is provided a winding device for the simultaneous formation and attachment of a loop to an apertured device, in which the loop is formed from a loosely structured fibre bundle of twisted yarn, and the device has first and second apertures through which the loop can be taken, in which the winding device comprises:
means for holding the device stationary;
a holder for holding a supply of yarn;
a guide path for allowing the leading end of yarn to be withdrawn from the supply and to pass through the first aperture in the device in one direction and through the second aperture in an opposite direction, and thereafter moving away from the device so as to form a basic loop;
means for applying movement of the basic loop along the guide path simultaneously with withdrawal of further yarn from the supply so as to apply successive loop turns to the basic loop and thereby form a progressively increasing loop core; and,
means for applying relative twist between the loop core and each successive loop turn so as to form a cohesive looped fibre bundle attached to the device.